Marie-Louise Knuppert trained to become a union representative through the Trade Union Movement's Internal Training System and studied labour market policy and business organisation at the Open University, AUC, in 1993.

Knuppert has been a member of the Danish Confederation of Trade Unions (LO i Danmark) Day-to-Day Management since 2005 and a member of LO's General Council since 1999. She was elected Confederal LO-Secretary in 1996 and employed with LO's Aarhus County from 1992-96. She was elected president of the Union of Commercial and Clerical Employees in Denmark (HK) from 1984-96.

Knuppert sits on a number of boards, including: The LO-College Board, the LO/FTF (Danish trade union council for international development co-operation) Council, AOF (the Workers' Educational Association), The European Trade Union Confederation (ETUC) Executive Committee and is a Board Member of Danida (the Danish International Development Agency). She is also Chairman of the Board of The Workers' Museum and the Labour Market Holiday Fund, ATP.